function convert(list) {
	const res = []
	const map = list.reduce((res, v) => (res[v.id] = v, res), {})
  console.log('map: ', map);
	// for (const item of list) {
	// 	if (item.parentId === 0) {
	// 		res.push(item)
	// 		continue
	// 	}
	// 	if (item.parentId in map) {
	// 		const parent = map[item.parentId]
	// 		parent.children = parent.children || []
	// 		parent.children.push(item)
	// 	}
	// }
	return res
}
let list =[
  {id:1,name:'部门A',parentId:0},
  {id:2,name:'部门B',parentId:0},
  {id:3,name:'部门C',parentId:1},
  {id:4,name:'部门D',parentId:1},
  {id:5,name:'部门E',parentId:2},
  {id:6,name:'部门F',parentId:3},
  {id:7,name:'部门G',parentId:2},
  {id:8,name:'部门H',parentId:4}
];
console.log('convert(list): ', convert(list));